Another point, how would you explain that the integument of birds where
preserved correctly, while that of (nonavian) dinosaurs
wasn't?

In my last e-mail I forgot to add
that AFAIK the feathers of Liáoníng birds and near-birds look the same
(haven't seen specimens), and that even the feathers on the various pieces of
"Archaeoraptor" are genuine!

Concerning secondary
featherlessness and tyrannosaur scales -- what about a single mutation that
produced scutes all over the body instead of only on the
feet?

Actually, something very similar to this mutation is present in modern
chickens (they retain some feathers on the body, but look pretty darn weird: saw
them at the SICB Feathers meeting back in 1999). However, let us
remember that we most certainly do not yet know what the integument of all parts
of the body of a tyrannosaurid looks like (okay, to be fair we don't know for
certain what any of it looks like, until such time as the tyrannosaurid skin
impressions are presented in some sort of non-internet context where people can
evaulate them and see what they look like).

I
would not put it out of the realm of reason for there to have been scales in
some areas, scutes in others (the feet), and scaleless skin in still
others. We already know that the size and shape of scales in hadrosaurids
(for example) vary from different parts of the body, and furthermore we have
examples of modern theropods with naked heads, feathered bodies, and
scute-covered feet.

Even
further complications in reconstructing the physical distribution of feathers on
a given form:

*Feathers change in type (and in some cases distribution)
during ontogeny

*External appearances to the contrary, feathers do not
sprout out all over the surface of a birds body in the majority of modern
birds. Thus, feathers of modern birds are NOT arranged like mammalian
hair. Instead, they actually arise out of several tracks down parts of the
body, but based on their orientation from these tracks manage to cover the
surface of the bird. It would be interesting to find out if Mesozoic
coelurosaur feathers similarly grew in tracks, or if instead the basal condition
was more like hair in its anatomical distribution, and only later became
sequestered into certain parts of the skin.